Halogenated nitronaphthalene compositions



aEsme 25, 1946. F. M. CLARK HALOGENTED NITRONAPHTHALENE COMPOSITIONSFiled NOV. 23,' 1943 Inventor: Frank V'LClark y His Attorney.

Patented June 25, 1946 HALOGEATED NITRONAPHTHALENE COMPOSITIONS FrankClark, Pittsfield, Mass., assignor to General Electric Company, acorporation of New York Application November 23, 1943, Serial No.511,440

8 Claims. 1

The present application relates to chlorinated nitronaphthalenecompositions and is a continuation-impart of my earlier applicationSerial No. 466,021, led November 18, 1942 which in turn is acontinuation -oi' application Serial No. 355.588, led September 6, 1940.

It comprises new compositions suitable for dielectric and insulatingpurposes in electric capacitors, capacitance bushings, or other electricdevices, and in particular compositions consisting wholly or in part oftrichlor alpha nitronaphtha- Iene. My invention also includescompositions in which chlorinated nitronaphthalene is associated withhalogenated polyphenyl products as, for example, pentachlor diphenyl.

In the accompanying drawing Fig. 1 is a paper-spaced capacitor# shownpartly unrolled, as an example ci a device for the impregnation of whichcompositions embodying the present invention are suitable; Fig. 2 is agraph showing the relation of capacity to a range of compositionscontaining trichlor alpha nitronaphthalene; Fig. 3 is a graph .showingthe dielectric constants for a range of compositions made up ofpentachlor diphenyl and trichlor alpha nitronaphthalene; Fig. 4 is agraph showing the relation of capacity to temperature for a range ofcompositions embodying my invention; and Fig. 5 is a graph showv ing therelation to capacity to temperature for a specic composition madeinaccordance with my invention.

Capacitors ordinarily contain sheet material spacers or septa betweenmetal armatures, as for example capacitor linen or kraft paper.Capacitor spacers also may consist of derivatives of ce1- lulose, suchas sheets or tapes of cellulose acetate, Cellophane or cellulose ethers,as for.. example ethyl cellulose and its modifications. When coated orimpregnated with my new compositions, such spacers show surprisinglygood dielectric stability.

Chlorinated nitronaphthalenes like all nitro compounds, are notcharacterized by a high degree of chemical stability. When subjectedV toheat in the range of from 75 to 100 C. or to light, even at roomtemperature, these compounds'de-A teriorate chemically. Theydarken yincolor and increase in acidity and otherwise show a chemical change whichnormally would be expected to result in a high degree of electricalinstability in any dielectric assembly of which they might be a part.Surprisingly, the contrary has been found to be true. Electricalapparatus when impregnated with my improved dielectric compositions ischaracterized by a high degree of electrical stability and otherwise isWell suited for practical use. Trichlor alpha nitro naphthalene, inparticular, has been found to possess the best combination of propertieswhereby desirable characteristics are imparted to capacitors and otherelectric devices, as, high efficiency, long life and desirabletemperature-capacity characteristics.

In preferred compositions embodying my invention trichlor alphanitronaphthalene constitutes aromatic compounds.

at least about l0 per cent and up to about 40 per cent of the entirecomposition. However, for

some purposes the content of such chlorinated alpha nitronaphthalene maybe as high as 60 per cent and in other cases may be as low as a fractionof one per cent.

Compositions consisting mainly of mixtures of alysvt should be present,for example, iron, antimony, iodine or aluminum. Chlorination iscontinued until the amount of combined chlorine as determined by thespecic gravity or the weight of a sample of the product has reached avalue .corresponding to a desired chlorination product.

For example, trichlor alpha nitronaphthalene may be prepared by thefollowing procedure:

To 1780 parts byweight of alpha nitronaphthalene is added a suitablecatalyst, such for example as about 5 parts of comminuted iron. Themixture is heated to produce fusion which takes place at a temperatureof about to 70 C. chlorine gas is bubbled through the fused mass. Thetemperature should be raised as chlorination proceeds. The followingschedule is a general guide.

When the increase in weight of the product indicates that thechlorination has progressed to about one to two atoms per molecule(abouty 22 per cent chlorine), the chlorination is somewhat slowed. Inorder to accelerate the reaction the temperatureis raised to about to 90C. When the total combined chlorine corresponds to about 2.5 atoms permolecule (about 34 per cent chlorine), the reaction temperature shouldbe raised Preferably a suitable cat-v l addition of modifyingingredients.

38 per cent chlorine in combination. This is the,

by evaporation until crystals of trichlor alpha` nitronaphthaleneseparate therefrom. These crystals are removed by filtration, or othercon venient way, and dried in air or under vacuum or other known method.The crystalline product at this stage has a melting point of about 132to 135 C. It is-.suitable without further purification for manyelectrical uses. For some purposes a more highly purified product may bedesirable. This can be obtained by recrystallization. The melting pointof the pure product is about 155 C.

Alternatively, the chlorination may proceed in the presence ofv an ironcatalyzer until approximately 38 per cent of chlorine has beenintroduced. At this stage most of the product will consist of trichloralpha nitronaphthalene. Some tctrachlor and some dichlor alphanitronaphn thalene may be Present inthe chlorination prod.- uct. Themixture may be purified by distillation. It has a boiling point in therange of 230 to 280 C. at a pressure of millimeters of mercury. Theyield'obtained is about 80 to 90 per cent. l':rer sumably because of thepresence of small amounts of dichlor andv tetrachlor products, thedistillate cools to a non-crystalline, resinous solid at roomtemperature having the following characteristics.

Color light yellow Flow point a'. l0 to 15 C.

Viscosity at 98.9 C--- 50 to 55 seconds Saybolt Universal Bpeclilogravity at 100 C. 1.555 to i565 The distillation product may be refinedby conitact with a .suitable absorbent, such as fullcrs earth.preferably at 100 C. The product after nltration has the followingaverage properties.

Color u light yellow Flow point '10 to 75 C. Viscosity 54 secondsBaybolt Because of its non-crystalline condition, this composition iswell adapted for the impregnation of high voltage capacitors evenwithout the l For the purification of some chlorinated produots. asolution process is preferable. The -chlorinated product is dissolved ina suitable solvent, auch, carbon tetrachloride or trichlorbenzene. Thesolution is ltered free from the` suspended catalyst if the catalyst isinsoluble in the solvent which is employed. The solution is washed withwater and, if somewhat acid, is washed with dilute sodium hydroxide (3to 5 per cent solutim) and is again washed with water to remove 4 tracesof the hydroxide. Purification by distillation may be practised. Somedecomposition may occur of the product being distilled. In that case.the distillate should be purined and neutralized by washing with 3 to 5per cent solution of sodium hydroxide and dried by heating under reducedpressure.

Trichlor alphantronaphthalene can be asscelated advantageously withchlorinated diphenyl or equivalent hologenated polyphenyl compound.

By the term polyphenyl compound" I mean to than a. similar capacitortreated with. pentachlor diphenyl imassociated with a modifyingingredient.

Compositions containing up to about per cent of said trichlornitro-naphthalenc product. the remainder consisting of pentachlordiphenyl, not only result in a markedly higher capacity when used asimpregnants for paper-spaced ca pacitors than does such pentachlordiphenyl unassociated with the naphthalene compound, but otheradvantages accrue. Capacitors when impregnated with approximately 90parts pentachlor diphenyi associated with approximately l0 parts oftrichlor anitronaphthalene are characterizedA by a constant electricalcapacity over a temperature rango from about 25 to 100 C. Compositionsconsisting by weight of '75 to 90 parts of Dentaclilor diphenyl and 25to 10 parts of trichlor alpha nitrouaphthalene are liquid at roomtemperature, which is advantageous in the dielectric field. The mostdesirable proportion of the chlorinated nitro-naphthalene in adielectric composition deponds on the type of capacitor tissue,clampinr,1

pressure, etc., employed in the capacitor. In the results to bc given,the impregnated capacitors consisted of aluminum armatures separated byspacers of kraft capacitor paper. The latter has a thickness of .0004inch. This thickness is not critical but has been chosen as representinga prevalent commercial thickness. Such a capacitor is shown in Fig. 1,armatures being represented by the strips 2, 3. Two groups fl, 5 ofpaper spacers. are illustrated. The enclosing case is lnot shown.Electrical connection is made to the armatures by the tap straps E, l.The improved characteristics are indicated by graphs which will bepresently explained.

In the graph shown in Fig. 2, the abscissa represent a range ofpercentages, of the trichlor naphthalene compound, aNOnCiuHiCla, inadmixture of said compound with pentachlor diphcnyl and the ordinatesindicate in per cent a relative increase or decrease of capacity ascompared with a similar capacitor impregnated only with pentaclllordlphenyl. The graph l here shown represents results taken at C.capacitor tempera ture. Itwill be observed that although an increase ofcapacity occurs when even small additions of the naphthalene compoundare present. the capacity rises to a. maximum when the per centage ofthe naphthalene compound is between about 30 to 40 per cent.

As shown in Fig. 3, the dielectric constant of rises at 25 C. toapproximately 675 and at 100 C. rises to approximately 5.8 beforedecreasing.

When capacitors impregnated with `compositions embodying my-ivention areto be used under such. conditions /or-'in such circuits that thevarationif'capacit/y would produce an undel ever, from to 5 per cent ofthe chlorinated sirable ei''ect, then the naphthalene compound should berestricted to a range of about 10 to 20 per cent. As shown in the graphIl of Fig. 4, there is no 'change in capacity over a range oftemperature from about 25 to 100 C. when the percentage of aC1cH4ClaN0zin the mixture is about 10 per cent. The graph Il crosses the zero linewhen 10 per cent of the latter nitrochlor compound is present in themixture.

While I have illustrated my invention with 'particular reference tocompositions of chlorinated alpha nitro-naphthalene and pentachlordiphenyl, it is not restricted to such examples. Other chlorinatedpolyphenyl compounds can be similarly associated with the chlor alpha.nitronaph-thalene. For example, dielectric blends of trichlorl alphanitronaphthalene and tetrachlor diphenyl have advantageous dielectricproperties. Fig. 5 of the drawing, the graph l2, illustrates the veryslight changes in capacity of a capacitor containing such blend over thetemperature range 25 to 100 C. When impregnated with a dielectriccomposition made up oi' about 15 per cent of trichlor alphanitronaphthalene and 85 per cent tetrachlor diphenyl, a substantiallyconstant capacity results over this range. For many applications,especially in radio circuits, such constan-t capacity feature is ofparticular value.

The most advantageous compositions will vary in the ratio oi componentsdepending on the particular components chosen. For example, to secureconstancy of capacity in a composition containing pentachlor diphenyl,10 per cent of the nitrochlor compound is required, whereas` in acomposition comprising tetrachlor diphenyl per cent of the nitrochlorcompound is required.

- I also have found very small amounts of the chlorinated alphanitronaphthalene when associated with other dielectric material to beuseful ,as a stabilizer, particularly for high temperature operation.

When capacitors impregnated with chlor diphenyl, chlor diphenyl oxide orchlorinated diphenyl methane are placed on direct current voltage at astress in the range of 500 to 1000 volts per mil (which is used in manycominercia). applications), the capacitor is characterized by anunsatisfactory short life at temperatures of the order of 90 C. andhigher. For practical purposes, as for example in the case of manyillter -or blocking capacitors, operating temperatures in the range of90 C. and highereven to 110 C., are encountered. The failure of ordinarychlorinated polyphenyl capacitors in this temperature range isaccompanied by the etching and corrosion of the toil. When. howalphanitro-naphthalene is present, this foil corrosion is substantiallyeliminated with resulting dielectric stabilization of the capacity and acommercially satisfactory lengthof life.

ACapacitors impregnated with a composition including about 99 parts ofpentachlor diphenyl and 1 part of /trichlor alpha nitro naphthalene arecharacterized by a power factor at 25 C. in the range of:30 to .35 percent, and a direct current resistance value at least as high as 6000megohm-microfarads- Capacitors impregnated with a dielectric compositionconsisting of 95 parts of pentachlor diphenyl and 5 parts of trichloralpha nitronaphthalene similarly possess advantageouselectrical-characteristics. Capacitors impregnated with eitherimpregnant vfunction satisfactorily on direct current voltage" understresses as high as 1000 volts per mil without dangerous loss inresistance or-'i increase in power factor.

What I claim as new and desire to secureby Letters Patent of the UnitedStates is:

1. A non-crystalline, light yellow, resinous material composedessentially of trichlor alpha nitronaphthalene, said material having aflow point of about to '75 C., a dielectric constant -of about 8, apower factor at 60 cycles, 25 C. oi.'

about .13 per cent and a resistivity at said temperature of 29X 1012ohms per centimeter cube.

2. A composition of matter consisting essentially of chlorinateddiphenyl and trichlor alpha nitronaphthalene, the latter ingredientbeing present in the range of about 10 to 40 per cent.

3. A dielectric material consisting by weight of about to 90 per cent ofpentachlor diphenyl and about 25 to 10 per cent of trichlor alphanitronaphthalene.

6. A liquid dielectric material whichis suitable for capacitorimpregnation consisting by weight of parts of pentachlordiphenyl and 15parts of trichlor alpha nitronaphthalene.

'1. A liquid dielectric material which is suitable for capacitorimpregnation consisting mainly oi' a chlorinated polyphenyl compoundwhich is admixed with at least about one-half of one per cent oftrichlor alpha nitronaphthalene.

8. A non-crystalline, resinous material having a ilcw point-of about 70to '15 C. composed essentially of trichlor alpha nitronaphthalene andcontaining as impurities amounts o! dichlor and tetrachlor alphanitronaphthalene which are insuflicient to cause the boiling point ofthe composition to depart from a normal range of about 230 to 280 C. ata pressure lci' 15 mm. of mercury.

FRANKMCIARK.

